Water in Mariner 40hp gearbox

[scubadave]

Hi
Ive just drained the gear oil on my mariner 2 stroke 40hp, 1990s and found about a third of the fluid was water?
Any ideas which seals could be faulty? Or is this a common problem?
The other problem i have with it is the idle speed. It seems to run very fast on tick over causing the gears to crunch slightly when putting it in gear.
Never had much to do with outboards so and info is gratefully received.

[uncle al]

Has the drain plug and level plug washers in good condition?Is a washer missing from one of the plugs?You need to preasurerise the gear housing to about 8psi (there is a service tool available from any merc/mar dealer.When it is preasureised with the gear housing imersed in water rotate the driveshaft first and watch for bubbles or preasure dropping, if nothing seen there do the same with the propshaft, if still nothing seen pull/push the gear selecter rod and again check for preasure dropping or bubbles.
As regards your tickover do you know what revs?Thing do go in with a bit of a clunk, was there any metal fillings in the oil that you drained?If so you have a problem.

[scubadave]

Hi uncle al. There didnt seem to be any metal in the gear oil. It just seems to be running quick and making me cringe when i put it in gear.
As for the gear housing, the washers look quiet new so i will have a look for a pressure tester and see what i find. thanks

[Locozodiac]

Seems time for a complete lower unit kit change, includes all parts needed. With respect being rpm to hight at idle, with warm engine adjust idle screw CCW to lover engine rpm, adjust enought to hear a dry clack when gearing forward and engine does not die, adjust as needed.

Happy Boating

[matt h]

take the prop off and check the shaft seal. there could be fishin line caught around the seal causing it to split. as said above. check the two fibre washers on the 1 drain plug at bottom and 2 the fill plug..should be replaced every time you change gear oil which should be done annually.
when you do sort it all out, re fill the gearbox from the bottom and let it spill out at the top plug.

[HughN]

Today I discovered the same thing on my Mariner (Yamaha) 30 - in fact there was no oil in there at all - just seawater.

If the driveshaft oil seal under the water pump was a bit weak could water have been pushed through the gearbox and forced oil (and then water) past the propshaft seal?

Still, it'll be very clean to work with when I take it apart.

[spartacus]

Originally Posted by HughN

Today I discovered the same thing on my Mariner (Yamaha) 30 - in fact there was no oil in there at all - just seawater.

I've seen emulsified oil (goes like mayonnaise) when water is present, but no gear oil, that's got to be a first. Goodness knows what damage is likely to have happened without lubrication.

You'll need to use a neutralising solution to ensure all the salt crystals are dissolved in the gear case. White vinegar will do, then warm water and baking soda to remove any acidity. Run some Duck Oil penetrating lube through it, and drain.

I'd use general purpose gear oil in it to lubricate initially, then replace water pump seals and prop-shaft seals. I'd also pressure test it to eliminate the possibility it's leaking somewhere else. Renew fill and drain plug washers. If all airtight, then drop the oil (checking for metal fragments) and renew with Yamlube or Quicksilver gear oil.

No guarantee this will work, but it's either that or a new lower gear case unit.

[uncle al]

water in the gear housing, If it was mine I would strip it down examine gears and bearings rebuild with new seals and gaskets, probaly fit a new water pump impeller at the same time, and dont forget to put about 8psi into the gear housing and work the shafts,turn the drive and prop shaft, move the gear selecter shaft in and out of gear, Please keep in mind that service tools may be required to do the above.

[HughN]

Thank you, Gents.

I think the service tools might be those for removing the cover-nut and the slide hammer adapter for removing the shaft.

I'm just off for a lie-down and some sedatives, having had a retrospective attack of the heebie-jeebies about all the places the boat has been in the 12 months since the last oil change...

[scubadave]

Thanks for all the info gents.
I will have a look at the seals over the next few weeks and report back with what i find.

[beamishken]

If your not going to do anything imediately fill the box with oil to keep oxygen out any cheap engine oil will do but dont use diesel as it contains moisture
If you dont protect from oxygen everything will be a rusty mass in days once you drained the water